In thermal printing, it is generally well known to render images by heating and pressing one or more donor materials such as a dye, colorant or other coating against a receiver medium. The donor materials are provided in sized donor patches on a movable web known as a donor ribbon. The donor patches are organized on the ribbon into donor sets, each set containing all of the donor patches that are to be used to record an image on the receiver medium. For full color images, multiple color dye patches can be used, such as yellow, magenta and cyan donor dye patches. Arrangements of other color patches can be used in like fashion within a donor set. Additionally, each donor set can include an overcoat or sealant layer
It will be appreciated from this that in conventional thermal printers the size of the donor media patches defines the maximum size of full size image that can be printed using thermal printer. To provide flexibility of use, many thermal printers are capable of printing relatively large images such as 6″×8″ images. While prints of this size are highly desirable for many uses, it can be challenging to use and store images printed at this size. Accordingly, consumers often request that such printers render images at a fraction of the full size image, such as images printed at the wallet size, 3″×5″ size or 4″×6″ size. Images at these sizes are more easily used and stored and require only a fraction of the donor material from a donor patch set.
Unfortunately, most printers of the prior art are not adapted to efficiently use the donor material from the fractional donor patch set for printing other images. Instead, it is conventionally known to have a thermal printer advance to the next complete donor set after printing a fractional size image so that the thermal printer is prepared to print any size image when the next printing order is received. It will be appreciated that this results in inefficient use of the donor material by causing increased printing costs. What is needed therefore is a method and system that enable more efficient use of donor material in a printing system.
It will also be appreciated that many printing systems are adapted so that they can receive a variety of different donor ribbons and that it is not unusual for a donor ribbon to be removed from a printer when only some of the available donor sets on the donor ribbon have been used or partially used for fractional size printing. However, a problem can occur when such a partially used donor ribbon is reinstalled into a printer. Specifically, it will be appreciated that the printer often has no knowledge of whether the donor ribbon is positioned in the printer such that the printhead is confronting a full donor patch set or a fractional donor patch set. Further, the printer has no knowledge of the number of full donor patches remaining on a donor ribbon or the number of fractional donor patches remaining on a donor ribbon.
Such information can be tracked and manually provided to the printer, however, such a manual process introduces the prospect of human error and adds labor costs. Accordingly, a wide variety of prior art systems attempt to use encodements, markings, memory devices and more recently radio frequency identification tags to store data from which a printer can determine the location of unused donor material set on a donor ribbon. This however, requires that the printer is adapted with special readers and/or writing equipment to read and/or write the marking.
What is needed therefore is a printer that is adapted to directly detect whether a donor patch on a donor ribbon has been loaded with one or more donor set with a full donor patch area available, a fractional donor patch area available or an unused donor patch area available.